1. Field of the Disclosure
This specification relates to a stabilization system for a satellite tracking antenna using a gyro and a Kalman filter, and a stabilization control method for the satellite tracking antenna.
2. Background of the Disclosure
A satellite-directing antenna or a satellite tracking antenna refers to an antenna which is used to communicate with an artificial satellite, which is located in the earth's orbit. The satellite tracking antenna is diversified in type, according to structure, purpose of use, functionality and the like.
The most widely known satellite tracking antenna is a civilian model satellite antenna which is generally installed in home or in a vehicle to be used for receiving broadcasts. A household satellite-directing antenna is fixed to direct the satellite. Such antenna does not require a separate manipulation after its initial installation. On the other hand, when an antenna, such as a vehicle-mounted satellite tracking antenna, is installed in a mobile (movable, moving) object (or vehicle), the antenna should continuously direct the satellite during movement of the moving vehicle. Hence, there is a requirement for an algorithm using a separate driving device for the antenna to direct the satellite with overcoming disturbance applied to the antenna. However, since even the vehicle-mounted satellite tracking antenna generally uses electric waves for receiving broadcasts with a relatively wide beam-width, it does not have to accurately track the satellite.
In the meantime, a communication network is very important for a military satellite antenna. The military satellite antenna has differences from the civilian model antenna, in the aspects of an operation environment, a used frequency, a required accuracy, and the like, depending on changes in environments of battlefields. More concretely, the military satellite antenna, which is mounted to a is military mobile device, suffers from severe disturbance and a narrow beam-width of a used frequency, and accordingly requires very high satellite tracking accuracy. Hence, in order to continue communication by allowing the military satellite antenna to keep tracking the satellite even in such operation condition, a stabilization control for the satellite tracking antenna is very important.
As a stabilization control method of the satellite tracking antenna, an algorithm using a posture of a platform, a sensor for measuring disturbance, and a beacon signal is the most widely used.
The stabilization control algorithm decides a satellite tracking direction by determining a posture of a platform. Here, it is difficult to accurately track the satellite due to the affection of a performance of a sensor, a mechanical characteristic, and the like. Accordingly, the satellite is tracked in such a manner of scanning a point with the highest strength of a beacon signal sent from the satellite. Afterwards, a control command for stabilizing the antenna is generated by measuring disturbance, which is applied to the antenna due to the platform being driven. In addition, a process of continuously tracking the satellite by detecting the point with the highest strength of the beacon signal in a continuous manner is used.
However, this algorithm has a difficulty in ensuring a stabilization control performance, due to accuracy of a disturbance measuring sensor, a mechanical characteristic of a pedestal of the antenna, noise of the beacon signal, a time delay, and the like.
To overcome those disadvantage, a stabilization control method using a monopulse satellite tracking antenna, which allows a pointing-error to be generated directly from a reference signal, which is sent from the satellite, is irrespective of the accuracy of the disturbance measuring sensor, is actively researched.
In the stabilization control method using a monopulse signal, in which a satellite pointing-error is output without using a sensor-measured value, after initially directing the satellite, the disturbance/posture measuring sensor and the pedestal characteristic do not affect the accuracy of the stabilization control. However, in many cases, the monopulse signal itself has already been distorted due to noise, a time delay, and the like. Specifically, when a monopulse antenna is applied to satellite communication, through which a reference signal of a weak strength is received, noise is also amplified while amplifying the signal, and a time delay is accordingly caused while processing the signal. Further, such problems become worse when a reflector of the satellite tracking antenna is designed to be small in size.